Abstract
The determination of the optimum harvest date (OHD) for long term storage is crucial for delivering high quality fruit throughout the whole marketing period. At present, the OHD for apples is identified through the assessment of conventional ripening parameters such as starch degradation pattern, endogenous ethylene, fruit firmness, total soluble solids content and background color. The interpretation of these parameters helps estimate physiological changes during maturation and ripening, though these parameters could also be influenced by environmental and agronomical factors. Molecular biology could possibly offer a new instrument for earlier and more accurate determination of OHD, through the investigation at the molecular level of the expression of some marker-genes, related to key ripening processes in maturing apples (NSure, The Netherlands). Another alternative way to complement further the existing conventional maturity tests could be provided by the optical chlorophyll index I DA (DA-Meter, Sinteleia, Italy), measured non-destructively, based on optical interactance measurements with the outer layers of the fruit. Experimental work has been carried out over a period of 3 years on two apple cultivars 'Gala' and 'Golden Delicious'. The purpose was to compare the influence of OHD as determined by conventional parameters with the OHD determined by the gene expression assay 'NSure' or by the optical index I DA on the fruit quality after controlled atmosphere storage. The results obtained demonstrate the high potential of the genomic approach and of the non-destructive chlorophyll assessment for maturity determination. Further work is necessary to link gene expression information to quality-change models in postharvest. The relevance of the DA-index is discussed in the light of most recent research.